Oil in water analyzer

ABSTRACT

An oil in water analyzer for measuring the concentration of hydrocarbons in an effluent stream. The oil in water analyzer has a valve system for acquiring a sample from an effluent stream. An extraction device is used for mixing a known volume of a solvent and the sample to produce a hydrocarbon/solvent mixture. A second valve is used for transporting the hydrocarbon/solvent mixture to a spectroscopic cell. It is at the spectroscopic cell where the concentration of hydrocarbons in the hydrocarbon/solvent mixture is evaluated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application which claims thebenefit of and priority to U.S. Provisional Application Ser. No.61/302,334 filed Feb. 8, 2010, entitled “Oil in Water Analyzer,” whichis hereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None

FIELD OF THE INVENTION

Oil in water analyzer for analyzing the quantity of oil in an effluentstream.

BACKGROUND OF THE INVENTION

The production of oil from underground reservoirs results in crude oilcontaining varying amounts of water generally in the form of awater-in-oil emulsion. It is general practice to dehydrate the crude oilby allowing it to stand but oftentimes the dehydration is enhanced bythe addition of a demulsifier to break the emulsion facilitatingphysical separation of the crude oil from the water. Following thisdehydration step, the crude oil is transported to the refinery where itmay undergo an initial dewatering procedure and/or subjected to theprocess of desalting, i.e. the removal of salts from hydrocarbon crudeoil, sometimes employing the action of an electrocoalescer.

Salts in hydrocarbon crude oil are generally dissolved in small dropletsof water or brine dispersed throughout the crude. Sodium chloride is theprimary salt followed by calcium chloride, magnesium chloride and thesulfates of these three metals. The total salt content ranges fromsubstantially zero to several hundred pounds per thousand barrels ofcrude.

These brine droplets are generally prevented from coalescing andsettling by a tough, elastic film at the surface of each droplet. Thisfilm is stabilized by natural emulsifiers found in the crude, solids,and solid hydrocarbons that concentrate at the droplet surface. Adesalting chemical or demulsifier displaces these natural emulsifiersand solids and weakens the film so the droplets of brine can coalescewhen they contact each other.

A new oil field will frequently produce crude with negligible water andsalt. As production continues, the amount of water produced increases,raising the salt content of the crude. Additional salt contaminationoften occurs during tanker shipment. An empty tanker takes on sea wateras ballast and often uses it to wash the tanks. To minimize pollution,the top, oily layer of ballast water and the washings are segregated ina slop compartment when the ballast water is discharged. Fresh crude isthen loaded on top of this slop oil and water. The entire compartment isthen offloaded at the refinery.

As earlier inferred, some brine can be removed by settling and waterdrawoff in the refinery's crude storage tanks. Some demulsifiers arevery effective in increasing the rate and amount of settling as well aspreventing sludge buildup and in cleaning tanks where sludge has alreadyaccumulated. Typically, the demulsifier formulation is injected into theturbulent crude flow as it fills the storage tank at a treat rate offrom 10 to 500 ppm. The settled brine is drawn before the crude ischarged to the pipestill.

To enhance the effectiveness of electrostatic desalter, desaltingchemicals are used in combination with an imposed electric field.Desalting chemicals are usually a blend of surface active materials inhydrocarbon solvents. These materials are preferentially absorbed at thebrine droplet surface, displacing the solids and natural emulsifiers.This greatly weakens the film around the droplets. The brine dropletscan then coalesce with the wash water (thus diluting the brine) and withother droplets so their size becomes large enough to settle by gravity.Depending on its composition and solvent, the desalting chemical mayalso dissolve the film.

To overcome solids stabilization of an emulsion, a good demulsifierformulation will cause the oil-wet solids to become water-wet and settleinto the water phase where they are removed with the effluent water. Asurfactant can also be used alone or in combination with the demulsifierfor this purpose. These chemicals work by attaching an oil-loving orsolids-loving section of the molecule to an oil-wetted solid. Awater-loving section then physically drags the solid into the waterphase. These molecules can also agglomerate solids to speed theirsettling. Without chemical treatment, most oil-wet solids will stay inthe oil phase even though their density is higher.

With the rising value of petroleum products, it becomes increasinglyimportant that separator equipment utilized by the petroleum industryextract the maximum possible recovered petroleum products from oil andwater emulsions and dispersions. These are main issues that currentlyaffect the profitability and operating integrity related to oilcarryover in effluent water streams from dewatering/desalting systems.

There exists a need to continuously monitor the oil carryover ineffluent water streams to ensure that maximum profitability can bemaintained.

SUMMARY OF THE INVENTION

An oil in water analyzer for measuring the concentration of hydrocarbonsin an effluent stream. The oil in water analyzer has a valve system foracquiring a sample from an effluent stream. An extraction device is usedfor mixing a known volume of a solvent and the sample to produce ahydrocarbon/solvent mixture. A second valve is used for transporting thehydrocarbon/solvent mixture to a spectroscopic cell. It is at thespectroscopic cell where the concentration of hydrocarbons in thehydrocarbon/solvent mixture is evaluated.

An alternate embodiment provides a method for continuously altering theprocess based upon the concentration of hydrocarbon material in thesample. The method begins by producing an effluent stream. A sample isacquired from the effluent stream then transferred into an extractiondevice. A known volume of a water-immiscible solvent is injected intothe extraction device. The sample and the water-immiscible solvent arethen mixed in the extraction device. The hydrocarbon component of thesample is extracted into the water-immiscible solvent to produce ahydrocarbon/solvent mixture which is transported to a spectroscopiccell.

In yet another embodiment the oil in water analyzing method begins withproducing an effluent stream from a dewatering/desalting operation. Inthis embodiment the effluent stream flows through a sample loop. Fromabout 0.5 mL to about 50 mL of a sample of the effluent stream istrapped in the sample loop. This sample is then transferred to anextraction device with the assist of a pressurized gas. A known volumeof toluene is injected into the extraction device. Air is then flowedthrough a venturi to create a pumping action to produce ahydrocarbon/solvent mixture from the sample. The hydrocarbon/solventmixture is then transferred to a spectroscopic cell with a water assist.The hydrocarbon concentration of the hydrocarbon/solvent mixture isdetermined by spectroscopy techniques. The leftover hydrocarbon/solventmixture and water are then transferred to a waste removal port with theassist of pressurized gas. An amount of toluene is injected into thesystem to solvent rinse the oil in water analyzer. In this method theoperation of the dewatering/desalting operation is adjusted based uponthe concentration of the hydrocarbon material in the sample.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further advantages thereof, may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings in which:

FIG. 1 depicts step 1 of how a sample is tested in the analyzer.

FIG. 2 depicts step 2 of how a sample is tested in the analyzer.

FIG. 3 depicts step 3 of how a sample is tested in the analyzer.

FIG. 4 depicts step 4 of how a sample is tested in the analyzer.

FIG. 5 depicts step 5 of how a sample is tested in the analyzer.

FIG. 6 depicts step 6 of how a sample is tested in the analyzer.

FIG. 7 depicts step 7 of how a sample is tested in the analyzer.

FIG. 8 depicts step 8 of how a sample is tested in the analyzer.

FIG. 9 depicts an embodiment of a first modified valve.

FIG. 10 depicts an embodiment of a second modified valve.

DETAILED DESCRIPTION OF THE INVENTION

The present embodiment describes an oil in water analyzer. The oil inwater analyzer has a valve system for acquiring a sample from aneffluent stream. An extraction device is used for mixing a known volumeof a solvent and the sample to produce a hydrocarbon/solvent mixture. Asecond valve is used for transporting the hydrocarbon/solvent mixture toa spectroscopic cell. It is at the spectroscopic cell where theconcentration of hydrocarbons in the hydrocarbon/solvent mixture isevaluated.

The valve system can be a single valve or an assortment of valves thatare connected together in a manner to acquire the sample from theeffluent stream.

The present embodiment additionally provides a method for continuouslyaltering the process based upon the concentration of hydrocarbonmaterial in the sample. The method begins by producing an effluentstream. A sample is acquired from the effluent stream then transferredinto an extraction device. A known volume of a water-immiscible solventis injected into the extraction device. The sample and thewater-immiscible solvent are mixed and the hydrocarbon component isextracted. The hydrocarbon/solvent mixture is then transferred to thespectroscopic cell via a water assist.

A water assist is a situation where water is flowed through a tube andused to push a sample, in this scenario a hydrocarbon/solvent mixture,from one area in the tube to another area.

In yet another embodiment the oil in water analyzing method begins withproducing an effluent stream from a dewatering/desalting operation. Inthis embodiment the effluent stream flows through a sample loop. Fromabout 0.5 mL to about 50 mL of a sample of the effluent stream istrapped in the sample loop. This sample is then transferred to anextraction device with the assist of a pressurized gas. A known volumeof toluene is injected into the extraction device. Air is then flowedthrough a venturi to create a pumping action to produce ahydrocarbon/solvent mixture from the sample. The hydrocarbon/solventmixture is then transferred to a spectroscopic cell with the waterassist. The hydrocarbon concentration of the hydrocarbon/solvent mixtureis determined by spectroscopy techniques. The leftoverhydrocarbon/solvent mixture and water are then transferred to a wasteremoval port with the assist of pressurized gas. An amount of toluene isinjected into the system to solvent rinse the oil in water analyzer. Inthis method the operation of the dewatering/desalting operation isadjusted based upon the concentration of the hydrocarbon material in thesample. This adjustment is necessary to maintain the operation of thedewatering/desalting unit within specified oil concentration limits.

The oil in water analyzer can be used for a variety of purposes such aswaste water, food industry water, deoiling and other application.Preferably the oil in water analyzer is used in a dewatering/desaltingoperation.

In the dewatering/desalting of heavy (high specific gravity, highviscosity) crude oils, or lighter crude oils containing emulsionstabilizers in the form of clay, asphaltenes, paraffins and othersolids, the virgin crude oils are subjected to mixing with wash water inone or two stages, usually in horizontal contacting dewatering/desaltingvessels. When the recovery of every processable drop of oil is sought,it is particularly advantageous to continuously analyze the effluentstream containing the brine, the oil-emulsion under-carry including theoil-wetted solids that remain in the oil phase, and the intermittent mudwash solids.

The oil in water analyzer has the capability to measure 10 to 50,000 ppmof crude oil in water when utilizing ultra violet spectroscopicdetection. Other configurations implementing optional detectors(visible, infrared, and fluorescence spectroscopy as well as refractiveindex) will have varying capability and will be constructed to achieveapplication specific performance.

FIGURES

FIGS. 1-8 describe an embodiment of the present method. In FIG. 1 theeffluent stream is directed through the sample loop via V1A and V1B.Toluene and water are loaded into their respective syringe pumps andresidues from the previous samples are drained to waste.

FIG. 2 depicts the effluent stream flowing through valve VO. From about0.5 mL to about 50 mL of a sample are trapped between V3 and V2. Airpressure is used to blow the contents of the sample into extractionchamber via V2 and V3.

FIG. 3 depicts a pathway for the toluene to pick up any residual samplefrom the sample loop to the extraction chamber. It is in the extractionchamber where the sample and the known volume of toluene are mixed tocreate a hydrocarbon/solvent mixture.

FIG. 4 depicts feeding air via V4 and V5 into the extraction chamberthrough the venturi to create pumping action, thereby pulling thetoluene from the top of the extraction chamber. Excess air is routedthrough V7 to vent.

FIG. 5 depicts the reloading of the toluene syringe pump. Additionallywater is injected from syringe pump via V8 and V13 into the bottom ofthe extraction chamber to lift the hydrocarbon solvent mixture to aspectroscopic cell.

FIG. 6 depicts transferring the leftover hydrocarbon/solvent mixture andwater to a waste removal port.

FIG. 7 depicts injecting toluene through valves V11 and V6 to solventrinse the optical cells.

FIG. 8 depicts injecting air through valves V5, V6 and V9 to clear andevaporate rinsing solvent from the analyzer.

In one embodiment the operation can be set to a cycle as short as 7minutes. The cycles may be run consecutively or with delay depending onthe application need and solvent availability.

In one embodiment the method is completely automated. It only requiresreplenishment of solvent provided pressurized gas and water are obtainedfrom operations. Data can be automatically transferred to a distributivecontrol system (DCS), plant historian, or other database. Data can alsobe stored in onboard memory.

In another embodiment of the method the oil in water analyzer usesmodified valves. The first modified valve is shown in FIG. 9 wherein themodification would permit the sample stream to be routed through thebody of the valve, keeping the valve internal component clear.

The second modified valve is be shown in FIG. 10 wherein a stainlesssteel tube is connected to the valve and provides a path to perform asolvent rinse of the downstream side of the valve body and the oil inwater analyzer. In this embodiment the stainless steel tube is ⅛ inch indiameter.

The modified valves can be placed throughout the oil in water analyzeras needed.

Accordingly, the scope of protection is not limited by the descriptionset out above, but is only limited by the claims which follow, thatscope including all equivalents of the subject matter of the claims.Each and every claim is incorporated into the specification as anembodiment of the present invention. Thus the claims are a furtherdescription and are an addition to the preferred embodiments of thepresent invention. The discussion of any reference is not an admissionthat it is prior art to the present invention, especially any referencethat may have a publication date after the priority date of thisapplication.

The invention claimed is:
 1. A method comprising: a) producing aneffluent stream; b) acquiring a sample from the effluent stream; c)transferring the sample into an extraction device; d) injecting a knownvolume of a water-immiscible solvent into the extraction device; e)mixing the sample and the known volume of the water-immiscible solventin the extraction device; f) extracting a hydrocarbon/solvent mixturefrom the sample; g) transporting the hydrocarbon/solvent mixture to aspectroscopic cell; h) determining the hydrocarbon concentration of thehydrocarbon/solvent mixture by spectroscopy techniques; and i)continuously altering a dewatering/desalting operation based upon theconcentration of the hydrocarbon material in the sample.
 2. The methodof claim 1, wherein the effluent stream is from a dewatering/desaltingprocess.
 3. The method of claim 1, wherein the effluent stream compriseswater and a hydrocarbon material.
 4. The method of claim 3, wherein theamount of water in the effluent stream is at least 95 wt %.
 5. Themethod of claim 3, wherein the hydrocarbon material is at least 10 ppm.6. The method of claim 1, wherein the amount of the sample taken fromthe effluent stream ranges from 0.5 mL to 50 mL.
 7. The method of claim1, wherein the solvent is water-immiscible.
 8. The method of claim 1,wherein the solvent comprises a group of water-immiscible solventsconsisting of: toluene, xylene, substituted aromatics, mixed aromatics,mixed hydrocarbons, straight run gasoline, saturated hydrocarbons andhalogenated alkanes.
 9. The method of claim 1, wherein the spectroscopytechniques utilized consisting of: ultra violet spectroscopy, visiblespectroscopy, infrared spectroscopy, fluorescence spectroscopy andrefractive index.
 10. An oil in water analyzing method comprising: a)producing an effluent stream from a dewatering/desalting operationwherein a portion of the effluent stream flows through a sample loop ofthe oil in water analyzer, b) trapping from 0.5 mL to 50 mL of a sampleof the effluent stream from the dewatering/desalting operation withinthe sample loop; c) transferring the sample into an extraction devicewith the assist of a pressurized gas; d) injecting a known volume oftoluene into the extraction device; e) mixing the sample and the knownvolume of toluene in the extraction device; f) feeding air through aventuri to create a pumping action to extract an amount of a hydrocarbonfrom the sample into the toluene; g) transferring thehydrocarbon/toluene mixture to a spectroscopic cell with a water assist;h) determining the hydrocarbon concentration of the hydrocarbon/toluenemixture by spectroscopy techniques; i) transferring the leftoverhydrocarbon/toluene mixture and water to a waste removal port with theassist of pressurized gas; and j) injecting an amount of toluene tosolvent rinse the oil in water analyzer, wherein the operation of thedewatering/desalting operation is adjusted based upon the concentrationof the hydrocarbon material in the sample.